Telephone system.



E. LAND.

TELEPHONE SYSTEM. memos FILED FEB. I3. 1905. RENEWED OCT. I8. 1906.

1,146,177. Patented July 13, 1915.

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TELEPHONE SYSTEM.

APPUCATION FILED rEe. i3. 1905. RENEWED 0:7. l8. I906.

1 ,146,177. Patented July 13, 1915.

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EDMUND LAND, OF GRAND RAPIDS. MICHIGAN, ASSIGNOB, BY MESNE ASSIGNMENTS, TO KELLOGG SWITCHBOARD & SUPPLY COMPANY, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented July 13, 1915.

Application filed February 13, 1905, Serial No. 245.844. Renewed October 18, 1906. Serial No. 339,577.

T all uv'mm it may (om-em Be it known that I, EDMUND LAND, a

citizen of the Dominion of Canada, and a resident of Grand Rapids, county of Kent,

: and State of Michigan, have invented a new and useful Improvement in Telephone Sys- =tems, of which the following is a speclfication.

My invention pertains to telephone stems in which automatic devices are used or connecting telephone lines, or for performing certain functions in the connection of telephone hnes. in addition to functlons performed manually by telephone operators at object of my invention to provide the automatic switches with a new and improved circuit by means of which circuit, applied to automatic switches of well known type,

' many of the parts now existing in those automatic switches are rendered useless, their functions being performed fully by those parts used in my improved circuits, thus rendering possible a much simpler and much impiroved type of the automatic equipment use I accomplish the results first outlined, by the use of automatic selecting switches in connection with the trunks and controlling keys or devices in connection with the erators switching equipment. I accom ish the further results by a novel circuit, ully shown in accompanying drawings.

In the drawings, Figure 1 shows the circuits; Fig. 2 shows mechanical operating details of the switch 53 of Fig. 1; Fig. 3 shows mechanical operating details of the switch of Fig. 1; Fig. 4 is a section through the main shaft 28 of Fig. 3, show ing detail of the ofl'mormal switch; and Fig. 5 shows a modification of the circuits of Fig. l in which the well lmown Strowger calling dial with its associated contact-making devices is substituted for the keys U4 and 95 of F1 1.

In Fig. 1, I have shown circuits adapted to be used in connection with automatic switches of the Strowger type as now commercia-lly used, that switch being of the general type covered b United States Patent No. 638,249, dated ecember 5, 1899, Keith, et al., assignors to the Strowger Automatic Telephone Exchange; the switch as disclosed in that patent has been modified as now used in the detail of its releasing mechanism, the operation of that detail now being as follows: A releasing electromagnet is provided which is energized upon the simultaneous energization of the vertical and rotary magnets or line relays; the releasing magnet has attached to its armature, a link adapted to engage a pin upon the pawl holding the part carrying the moving contact terminals; upon the energization of the releasing magnet, the armature advances the link and the link drops over the pin in the holding pawl, the pin in the holding pawl then prOJecting into or through a hole in the link, but as yet, the holding awl has not been moved; upon the de'energization of the releasing magnet, a retractile spring returns the armature to its position of rest and thus withdraws the link and thus actuates the holding pawl to withdraw it from engagement with the part carrying the moving contact terminals, permitting that part to return to its normal position of rest; the link attached to the armature of the releas ing magnet retains the pin upon the holding pawl and thus retains the holding pawl out of engagement with the part carrying the movable terminals until by the actuation of either the vertical or rotary magnet, the link is pushed from the pin and the holding pawl is thus permitted to return to its position in engagement with the part carrying the moving contact terminals, to retain that part in such position as may be determined by actuation of its driving pawls, both vertical and rotary.

I have invented circuits by which, when those circuits are applied to a modern Strowger automatic switch, only the vertical magnet, rotary magnet and releasing magnet are necessary, the releasing magnet being provided with armature contacts replacing, and therefore displacing also, the well known side-switch of the Strowger mechamsm.

At 10 in Fig. 1 are shown the circuits of an automatic switch of the fundamental type of the Strowger, but modified for the use of my circuits, and having, therefore, many of the Strowger features omitted. In Fig. 3 are shown the mechanical operating details of this switch, with an additional detail in Fig. 4. In these figures, 11 is the vertioal magnet, causing the vertical steps of the main shaft 28 through the action of its armature 206, pawl 207 and ratchet 201; 12 is the rotary magnet, causing the rotary steps of the shaft 28 through its armature 13, pawl 210 and ratchet 202; 1-1 is an electrical contact point connecting with the armature 13 of rotary magnet 12; 15 is the release magnet with its armature 212 and attached link 213, the link 213 having a hook 214 adapted to engage pin 205 011 pawl 203, the pawl 203 being pivoted at 2,04 and being adapted to engage the shaft 28by bot-h vertical and horizontal ratchets. When the armature 212 is attracted, the link 213 is advanced, the hook 214 passes] oyer thelpin 205 and all parts remain during the continuance of cnergizationof releasemagnet 15; upon the deenerglzation of them lease magnet 15, e armaturefflll is restored by its retractile spring,' drawingw it he link 213, causing the hook 21%}0 en age carry with it thepin 205, ;thif$" ii the pawl 203 from engagement with the two ratchets of the shaft 28,:3nd permitting the shaft 28 to return to its normal position of rest through the action of its springs'and gravity Link 2. .5 v A ma ur 206, will lift link 2l3upon he tir'st energization of vertical magnet 11 uhseqgent to disconnection, thus releasing pm and pawl 203. Attached tothe'armature 212 of release magnet 15 are electrical contactsprings 17, 20, 23, adapted when at rest t o make connection withcontact point'syl ifi, I9, 24, respectively, and Whenfthe armature is in its attracted posit'on ake connection with contact points 18,21,253, respectively. Part 25 is a' contact-spring associated, with a contactspring 26, the pair constituting an off-normal switch, held open by rib 27 on the shaft 28 and adapted to he closed at the first rotary movement of the shaft 28. Parts 29, 30 and 31 are the moving contact terminals or wipers supportedj insulatingly upon the shaft 28, and adapted to make contact with the fixed contact terminals,- or waiting contacts, 32, 33, 34, 35, 36, 37, etc., to effect circuit conditions as described later.

In the use of o my invention as herein shown. a jack 51 is located in the same central office with the switch 10, and associated with the jack 51 are thefsignal lamp 52 and the automatic selecting detice The selecting device 53 is an automatic switch having only one movement of selection, namely, a rotary one, the essential mechanical parts of which are shown diagrammatically in Fig. 2. In some telephone exchanges the distribution of central oiiices and traffic might require that the switch 10 be in a central oflice distant from the jack 51. in which case the principles of my invention apply equally well, the trunks extending from the switch 10 reachin either various portions of that central olfice, or extending to still other central ofiices, or both.

In Fig. 2, 54 is a shaft bearing insulatingly three movable contact terminals, or wipers (Fig. 1, 55, 56, 57), and bearing rigidly ratchet 58. 59 is an elcctromagnct energized by winding conductor 60 and controlling armature 61., pivotally sustained at 62 under tension of spring 65, and carrying upon its free end driving pawl 66, pivoted at 67, pressed by spring 68 and held from ratchet 58 by fixed pin 69; when magnet 59 attracts armature 61,,driving pawl 66 is propelled to engage ratchet 58 and to move said ratchet the distance of one tooth, further motion being prevented by fixed pin 70. Magnet 7 1, adapted tobe energized by Windingconductor 72, controls armature 73, pirotally' sustained at Z4, under tension of spring and bear ng nk 76, pivoted at 77, pressed by spring'78and with a downwardly projecting hook, '79; Holding pawl 80, pivotally sustained at $1 pressed by spring 3: engages ratchet 58 as shown, and

bears pro'jejcting pin 83. 'Link 7 6 has a cam edge84 extending over the face of ratchet 58, ndmtchetss carriesa pin adapted to'en age cam edge84 and to lift link 76. Link 6 issh'ownits lifted position. The electricarconnections and contacts of the switch andi arnialtures are not shown. The operation oft-he mechanical parts is as follows: Magnet, 59 is energized and released repeatedly; thus: propelling ratchet 58 and shaftfi'h'and'moving pin 85 away from link 76 niagnet 71tl1enis'energized, hooking proje'ction 79 over pin 83; upon the denergization-of relay 7 1 and release of its armature, holding pawl 80 iswithdrawn from engage ment with ratchet 58 which is returned to its position oil rest by yolute spring 89, attached to shaft-54 and fixed pin at return of ratchet to rest, pin 85 has engaged cam edge Slto lift link T6 from pin 83, restoring holding pawl 80 to engagement with ratchet-5s;

At 91 is shown the connecting plug of an operators equipment, the remainder of the equi ment heingof any well known or desire type; to this pin are connected the conductor 92 from the fiody of the plug to the grounded battery 93, and the two manually o erated keys 94' and 95; by the operation'o the key 9}, ground at 96 is connected to the ring conductor of the plug 97, and by the o eration of the key 95, ground is connected to the tip conductor of the plug 91.

The operation of the system thus shown is as follows: The telephone operator, having taken a call and having learned that the line called for is not terminated in the central oflice whose line terminals may be before her in multiple, or otherwise accessible, places the connecting plug 91 in the jack 51, or a similar jack similarly equipped; wipers 55, 56, 57 are in their position rest in contact with points 99, 101, 103 respectively; current flows from battery 93 through ele ments 9:2, 60, 59, 97, 98, 55 to ground at 99;

this energizes magnet 59, steps shaft 54 forward one step, advancing wipers 55, 56,

57 one step. so that wiper 55 now is in connection with waiting contact 100, and also magnet 59 breaks the circuit just described by its own armature contact and thus releases its own armature to complete the circuit as before, but now to ground through waiting contact 100, if that waiting contact be grounded, and so on repeating until a waiting contact without ground is connected with by wiper 55; assume that the first waiting contacttested, 100, is without a ground, then upon the closure of the armature contact of relay 59, current must flow from battery 93 through elements 92, 60, 59,

"72,, 71 and 121 to ground; the winding of magnet 71 is of comparatively high resistance, while the winding of magnet 59 is of comparatively low resistance, so that in the circuit now completed, the magnet 71-is sufficiently energized by its large number of turns to attract its armatures, yet the magnet 59 by its small number of turns-is insufficiently; energized and-1 does'not attract its armature; armature contacts of relay .71 therefore, are actuated and conductors 105 and 106 are connected to wipers -56fland 57 f and thence by waiting contactsllllfl'and st trunk conductors 107 and 108, respec- "may; also conductor 98' is disconnected from conductor :97 and connected to ground,

f thus placing ground upon waitingz contact 100 and upon trunk conductor 109; The lamp 52 is a signal lamp for the operator f who has inserted plu '91 into jack 51, and its operation is as fo lows: Beingin shunt by conductor 110 around the winding of magnet 59, the current flow through the lamp is proportional to theqflow through the circuits already considered, in which mag net 59 has formed apart.

The filament of-lamp 52 shall be so designed as to glow when ma et 59 is receiving such a current as will operate its armature; and not to glow when the current through magnet 59 is reduced to such an extent thatthe armature of said magnet is not operated; this requirement on the part of lamp 52 will cause lamp 52 to flash rapidly-or to glow continuously or variably during the vibrations of armature magnet which will continue until wiper has found a waiting contact without ground and magnet 71 is energized; at which time the re duction of current through magnet 59 will cause such a reduction of current through lamp 52 that the filament will not be heated to give an apparent signal. It is seen, thus, that when 0 erator in charge of plug 91 inserts the pug in jack 51, the lamp will glow until the automatic mechanism .33 has made selection and has connected with the conductor of a local trunk, such as 107 108-109. Conductors 107108 and 109 show a representative local trunk of a large number of similar local trunks, each of which trunks is connected to a modified Strowger switch as shown at 10, and each of which local trunks is terminated in branch multiples in many automatic devices, such as 53 connected to jacks such as 51. By the action of magnet 71 the conductor 98 has been grounded, and thus the waiting contact 100 has been grounded and ground has been placed upon all homologous contacts in other switches as 53, thus preventing connection with that trunk by any other such switch, since the presence of ground upon waiting contact 100 would pre vent the energization of magnet 71, and thus would cause magnet 59 to step the shaft 54 past this local trunk, and so on, until an idle conductor was connected with by wiper 55. The complete equipment of such an ofiice. therefore, consists of a, plurality of local trunks such as 107108 and 109, and

a plurality of selecting devices such as 53, each of the selecting devices having accessible, a plurality of said'local trimks, and being adapted when a plug is inserted into itsjack, as 51, to automatically test consecutively the trunks, to connect the jack with the first idle one found, and to isolate it by placing upon its waiting contact, as 100, in other switches, a ground which prevents that local trunk from being taken by any of the other switches. The operator, thus, by selectingvthe group of conductors 107-408 and 109 has selected an idle modified Strowger switch, as 10, and has appropriated it to her own use for this connection. The selection of that switch is announced to her by the permanent darkening of lamp 52, and she then may proceed to manipulate the automatic switch 10.

A plurality of switches as 10 are located in the same central ofiice, and from them extend trunks to other central offices; the arrangements of trunks being as follows: upon the first level of contacts shall terminate trunks for a given distant central ofiice; upon the next level shall terminate trunks for another given central oilice, and so on. for the different levels. Each level represents a different distant central oilice or a different division of such central oilice. In each level the trunks are similar and tenninate upon similar equipments at the distant central oilices, so that it is immaterial which of them be selected for service for a particular call, the selection merely depending on the necessity of taking a trunk not already in use.

The next step on the part of the operator at pin 91 is to select the proper distant central o co required to complete the call. This she does by the use of key 95. Upon ClOSlDg key 95, current flows from battery 93 through elements 111-11-112 1617- 107-- 56 105 114- 95 and to ground at 96, energizing vertical magnet 11, and stepping the mechanism of the modified Strowger switch up to the first level of waiting contacts in a manner well known in the art; the use of key 95 is repeated until the proper level is reached upon switch 10, then the key 94 is operated once. Upon the closure of key 94, current flows from battery 93 through elements 111-1171211819- 20 10S57-106--115116 to the ground at 96; energizing rotary magnet 12. Wipers 293031 are normally not in connection with any waiting contact. The energization of magnet 12 has broken the contact between parts 13 and 14 and has stepped shaft 28 forward one step, closing off-normal switch 2526, and carrying wipers 29 -303l into connection with waiting contacts at 32- 34-36 respectively. Upon release of key 94, the circuit through magnet 12 is broken and armature 13 is released, whereupon a circuit is completed for current from battery 93, through elements 111-11712 13-14-24-2329 to waiting contact 32 and to ground if that contact be grounded, as it will be if the trunk associated with that contact be already in use. Assuming that such trunk is in use, the circuit to ground at waiting contact 32 will energize magnet 12 again, attractingi armaturc 13 and stepping shaft 28 forward another step; this will ad- Vance wipers 29-3031 into electrical connection with waiting contacts 33-35-37 respectively, and such vibration of armature 13 will continue until wiper 29' reaches a trunk not already in use and whose waitin contact, as 33, therefore is not grounde Upon reaching an idle trunk, the circuit at wiper 29 is not grounded and path for current exists from battery 93 through elements 111-117-1213-14119l512026 25-10955 98 and to ground at 121, energizing magnet 15, but owing to the comparatively high resistance of magnet 15, and the comparatively low resistance of magnet 12, the magnet 12 is not energized to step the shaft 28 farther, nor to break its armature contact. The magnet 15, therefore, being energized attracts its armature and by the contact of parts 23 and 22', places ground upon the waiting contact 33 by the following conductors: 29--2322-12025109 55--121; thus, busy test is placed upon other waiting contacts in multiple with 33 to prevent other selective switches from connecting with the selected trunk. The energization of magnet 15 also operates to break contact parts 16 from 17 and 19 from 20, to make connections between elements 1718 and 20-21, thus connecting the conductors of the selected trunk directly to the conductors of operators connecting plug 91, and to her controlling keys 94-95, by the following conductors: 301&17-107-56 --105113114, and 31212010857 -106-115116; thus it is seen that the operator using the plug 91 is enabled to select the required distant central office by the manipulation of keys 95 and 94, and that the conductors leading from those kevs are car ried through to the distant central oflice so that by the further manipulation of those keys automatic switches either similar to the switch 10 or of the standard well known Strowger type, mav be operated to select further trunks or to select the desired subscribers'line. Many minor details may be modified or added for convenience without departing from the spirit or scope of my invention, for instance: Keys 94 and 95 may be replaced by the, well known Strowger calling device, or by any mechanism which automatically would give the proper num her of ground impulses upon the conductor 114, and then one upon the conductor 116. Further, only one of the Strowger calling devices might be used by the operator, it being switched from plug to plug by a key provided for each of the operators connecting plugs.

In lieu of the jacks as 51, and lamps as 52, with automatic selective equipments as 53, each trunk as107108109 may terminate directly in a jack as 50, or in a plurality of such jacks connected in branch terminal multiple. In the former instance the operator would connect directly withv switch 10 by taking the jack 50 with plug 91; in the latter case, the operator would, in the usual well known manner, test such jacks as 50 as might be before her, and having found an idle one would plug into it, and thus be connected directly with the selected switch, as 10 connected with that jack.

The outgoing trunk connected with the waiting contacts 333537 may terminate in the distant central oliice in manually operated switching equipments, instead of in automatic switches. For the purpose of illustration a trunk circuit T is shown extending from contacts 33, 35, 37, being equipped with a. well known form of supervision including tip and sleeve relays and a supervisory lamp. A line circuit L adapted for use with circuit T is also illustrated, being of a well known character and further reference thereto is believed unnecemary. Any signal to indicate to the operator at the coming end of trunk T may be employed, but I have shown a drop associated with the incoming end, it being adapted to indicate acall to the operator when connection is made with its associated trunk by a switch 10. Of course, it is to be understood that the application of my invention is not limited to any particular type of trunk, the one shown being merely for the purpose of illustration.

In each place where battery is shown in the circuit drawings accompanying this specification, a ground may be substituted, and where a ground is shown, a connection to a source of electric potential may be substituted, thus reversing the direction of the current flow, but not materially changing the system. Therefore, in view of the many possible modifications, I do not wish to limit myself to the specific details of apparatus designs, herein shown or described.

What I claim as new, and desire to seciu'e by United States Letters Patent is:

1. In a telephone system, the combination of an automatic switch, wipers and waiting contacts in said automatic switch, talking strands, an actuating magnet, means for op erating said magnet over a talking strand, a releasing magnet, a source of electric en ergy, said magnets and said source of energy being in series and said actuating magnet being adapted to operate only when said releasing magnet is shunted, and a shunt for said releasing magnet including in its circuit a wiper and a waiting contact for said automatic switch, substantially as described. 2. In a. telephone system, the combination of an automatic selective switch, a vertical magnet, a rotary magnet, switches by which the armature of said rotary magnet makes and breaks the circuit of the winding of said rotary magnet, and a release magnet adapted to be energized continuously throughout the duration of connection and adapted to restore all parts of said automatic selective switch to normal positions of rest upon its de'e'nergization, substantially as described.

3. In a telephone system, the combination of an automatic selective switch, an actuating magnet, a releasing magnet, normally open oilnormal contacts, means for closing said contacts, and a source of electric energy, said magnets said oil-normal contacts, and said source of electric energy being in series and said actuating magnet being adapted to op erate only when said releasing magnet is shunted, and a circuit adapted to shunt said releasing magnet, substantially as described. 4. In a telephone system. the combination of an automatic selecting switch, wiper-contacts and trunk-terminals in said automatic selecting switch, talking strands, an actuating magnet, means for operating said magnet over a talking strand, a releasing magnet, a source of electric energy, said magnets and said source of energy being in series and said actuating magnet being adapted to operate only when said releasing magnet is shunted, and a shunt for said releasing magnet adapted to be maintained while said wiper-contacts of the automatic selecting switch are testing busy trunk-terminals and adapted to be interrupted when said wiper-contacts engage trunk-terminals not already busy, sub stantially as described.

5. In a telephone system, the combination of a connecting plug, a jack adapted to be connected with by said plug, an automatic selective switch having one movement of selection associated with said jack and adapted to select and connect with an idle trunk when said plug is connected with said jack, a trunk terminating in said automatic switch and associated with another automatic selective switch in the same or other office having two movements of selection, groups of trunks terminating in said latter automatic switch and leading to other central olfices, means in said latter automatic switch for selecting first a group of trunks and then an idle trunk of that group, two conductors in said trunk, keys associated with said coimecting plug to control said latter selective switch over said two conductors, a third conductor in said trunk, circuitsincluding said third conductor and controlling the release and restoration of said first selective switch, circuits by which said latter automaticswitchis released by the restoration of said first selective switch, means by which said first selective switch is released by the disconnection ofrsaid plug from said jack, substantially as described.

6. In a. telephone system, the combination of a connecting plng, a jack adapted to be connected with by said plug, an automatic selective switch having one movement of selection associated with said jack and adapted to select and connect with an idle trunk when said plug is connected with said jack, a trunk terminating in said automatic switch and associated with another automatic selective switch in the same or other ollice having two movements of selection, a group of trunks terminating in said latter automatic switch and leading to another central ofiice, means in said latter automatic switch for selecting first said group of trunks and then an idle trunk of that group, two conductors in said first-mentioned trunk, keys associated with said connecting plug to control said latter selective switch over said two conductors, a third conductor in said trunk, circuits including said third conductor and controlling the release and restoration of said automatic switch, meansby which said latter automatic switch is released by the restoration of said first selective switch and means by which said first selective switch is released by the disconnection of said plug from said jack, substantially as described.

7. In a telephone system the combination of a central ofiice,a plug in said central oliice, switching devices adapted to connect with said plug, controlling keys associated with said plug, an automatic selective switch having two movements for selection and located in the same central oilice with said plug and switching devices, fixed waiting contacts in said selective switch, movable wiping contacts in said selective switch, other central olfices, trunks terminating on said wail ing contacts and extending to said other central offices, a local trunk terminating on said movable wiping contacts and extending to said switching devices adapted to connect with said plug, two conductors in said local trunk, circuits by which said controlling keys will be connected to said two conductors when said switching devices are connected to said plug, a third conductor in said local trunk extending from said automatic switch to said switching devices, circuits by which said third conductor is open at said switching devices when said local trunk is not connected with and by which said conductor is grounded at said switching devices when said trunk is connected with, a releasing magnet in said automatic switch, circuits by which said releasing magnet is connected between a grounded source of electric potential and said conductor after a trunk has been selected by said selective switch and with consequent energization of said releasing magnet, mechanical means by which the breaking of said circuits and consequent denergization of said releasing magnet will restore all parts of said automatic switch to their nor mal positions of rest, substantially as described.

8. In a telephone system the combination of a connecting plug, a jack adapted to be connected with by said plug, selective switch having one movement of selectiona-ssociated with said jack and adapted to select and connect with an idle local trunk when said plug is connected with said jack, :1 pair of wipers in said selective switches, a third wiper in said selective switch. an electromagnet in said selective switch, releasing means in said selective switch actuated consequent upon the deenergization of said electromagnet, armature contacts on said electromagnet adapted to connect two conductors of said jack with two of the said wipers while said electroniagnet is energized. armature contacts on said electromngnet adapted to connect said third wiper directly with ground while said electromagnet is energized. a circuit adapted to maintain the energization of said electromagnet, and to be broken by the removal of said plug from said jack, a local trunk terminating in said selective switch and associated with an automatic selective switch in the same office having two movements of selection, groups of trunks terminating in said latter automatic switch and leading to other central oflices, means in said latter automatic switch for selecting first a group of trunks and then an idle trunk of that group, two conductors in said local trunk, a third conductor of said local trunk, an electromagnet in said latter automatic switch, a pair of wipers in said latter automatic switch, a third wiper in said latter automatic switch, armature contacts on said electromagnet adapted to connect the said two conductors of said local trunk to said pair of wipers during the energization of said a electromagnet, armature contacts on said electromagnel: adapted to connect said third wiper to ground by a circuit extending through said third conductor of said local trunk during the energization of said electromagnet, and releasing and restoring means in said latter selective switch adapted to be actuated consequent upon the denergization of said electromagnet, substantially as described.

9. In a telephone system the combination of a central oflice, a plug in said central ofiice, switching devices adapted to connect with said plug, controlling keys associated with said plug, an automatic selecting switch having two movements for selection and located 'in the same or another central oflice, fixed waiting contacts in said selective switch, movable wiping contaicts in said selective switch, trunks terminating on said waiting contacts, a trunk terminating on said wiping contacts and extending to said switching devices adapted to connect with said plug, two conductors in said trunk, a third conductor in said trunk extending from said automatic switch to said switching devices, circuits by which said third conductor is open at said switching devices when said trunk is not connected with and by which said third conductor is grounded at said switching devices when said trunk is connected with, a releasing magnet in said automatic switch, circuits by which said releasing magnet is connected between a grounded source of electric potential and said third conductor after a trunk has been selected by said selective switch and with consequent energization of said releasing magnet, and mechanical means which will restore all parts of said automatic switch consequent upon the denergization of said releasing magnet, substantially as described.

10. In a telephone system, the combination of a central oliice, a plug in said central office, switching devices adapted M) con lid nect with said plug, controlling keys associated with said plug, an automatic selective switch having two movements for selec' tion' and located in the same or other central oiiice, fixed waiting contacts in said selective switch, movable wiping contacts in said selective switch, trunks extending from said waiting contacts to other switchdevices in the same or other central 0 ces, a trunk terminating on said wiping contacts and on said switching devices adapted to connect with said plug, two conductors in said trunk, a third conductor in said trunk, a releasing magnet in said automatic switch, a. circuit including the winding of said releasing magnet and said third conductor by which said releasing magnet is energized after a trunk has been by said selective switch, and mechamcal means for restoring said automatic switch consequent upon the denergization of said releasing magnet, substantially as described.

11. In a telephone system the combination of a connecting plug, a jack adapted to be connected with by said plug, selective switch having one movement of selection associated with said jack and adapted to select and connect with an idle trunk when saidplug is connected with said jack, a pair of wipers in said selective switch, a third wiper in said selective switch, an electromagnet in said selective switch, releasing means in said selective switch actuated consequent net, armature contacts on said electromagnet adapted to connect two conductors of's'aid jackwith two of the said wipers While sald electromagnet is energized, armature con tacts on said electromagnet adapted to connectsaid third wiper directly with ground while said electromagnet is energized, a-cirr cuit adapted to maintain the ener izationiof said electromagnet, and to be brohen by the removal of said plug from saidplu from said jack, a trunk terminating-Tin sai selecetive switch and associated with an auto: matic selective switch in the same orother central oflices having two movementsof selection, groups of trunks terminating in said latter automatic switch and leading to other switching devices, means-in said latter auto: matic switch for selecting first a groupof trunks and then an idle trunk of that group, two conductors in said trunk, a third condoctor in said trunk, an electromagnet in said latter automatic switch, a pair of wipers in said latter automatic switch, a third wiper in said latter automatic switch, armature contacts on said electromagnet adapted to connect the said two conductors of said trunk to said pain of wipers during the energization of said electromagnet, armature contacts on said electromagnet adapted to connect said third wiper to ground by a circuit throughsaid third conductor of said trunk during the energization of said electromagnet, and releasing and restoring means in said latter selective switch adapted to be actuated consequent upon the deenergization of said electromagnet, substantially as described.

12. In a telephone exchange system, interconnecting mechanism comprising a conductor, means under the control of the operator for establishing connection therewith, a plurality of trunks, automatic switch mechanism responsive to the establishment of said connection to automatically establish connection between said conductor and an idle one of said trunks, additional automatic switch mechanism associated with the distant end of the selected trunk for extending the circuit of said trunk, and means for releasing all of said automatic switch mechanisms by breaking the connection with said conductor.

13. In a telephone system, an automatic switch, a conductor extending to said switch, a plurality of trunks extending from said switch, a manual terminal for said eonductor, a plug for establishing connection with said tenninaL-operators meansassociated with said plug for directing the advance. of said switch to desired positions, means for subsequently causing said switch to automatically test said trunks and;.connect withlan idle one, a releasecircuit for said switch extending directly through contacts of the plugean, manual terminal, and meansdor restoring-saidswitch to. normal by interruptin said circuit upon withdrawing said plug fi'omsaid terminal.i.,j i 14. In .a telephone'system, anainterconnecting conductor-,ifav manual terminal and an automatic terminal at one end of said conductor, means associated with the; other end of said; conductor for extending the'circuitof said'conductor, manual means-for connecting to. said manual terminal, automatic switching means -f;'or connecting to said automatic terminal, and means responsiye to said manual connection to indicate busy at the automatic terminal.

15. In a telephone system, an interconnecting conductor, a manual terminal and an automatic terminal at one end of said conductor, an automatic switch associated with. the other end of said conductor, manual means for connecting to said-manual terminal, automatic switchin means for connecting to said automatic terminal, and means responsive to said manual connection to indicate busy at the automatic terminal.

16. Inv a telephone system, an intercon necting conductor, a manual terminal and an automatic terminal at one end of, said conductor, an automatic switch associated with the other end of said conductor, manual means for connecting to said manual terminal and causing the operation of said automatic switch, automatic switching means for connecting to said automatic terminal, means whereby said automatic switch may be controlled through said an: tomatic terminal, and means responsive to said manual connection to indicate busy at the automatic terminal.

17. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contact busy, a magnet and cotiperatlng means for advancing said active contact, relay-contacts, means for closing an initial energizin circuit for said magnet through certain 0? said relaycontacts to cause said active contact to advance a definite distance, means for closing a second energizing circuit for said magnet through other of said relaycontacts to continue the movement of said active contact, and means for actuating said relay-contacts to interrupt both of said magnet circuits.

18. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said pam've contacts busy, a magnet and coiiperating means for advancing said active contact, rclay-contacts, means for closing an initial energizing circuit for said magnet through certain of said relay-contacts to cause said active contact to advance a. definite dis tance, means for closing a second energizing circuit for said magnet through other of said relay-contacts to continue the movement of said active contact, and means for actuating said relay-contacts upon the engagement of said active contact with an idle passive contact to interrupt both of said magnet circuits.

19. In a telephone system, an automatic switch comprising passive contacts and a 00- operating active contact, means outside of said switch for rendering certain of said passive contacts busy, a magnet and 00- operating means for advancing said active contact, a control relay, means for closing an initial energizing circuit for said magnet through contacts of said relay to cause said active contact to advance a definite distance, means for closing a second energizing circuit for said magnet also through contacts of said relay to continue the movement of said active contact, and means for operating said relay upon the en agement of said active contact with an i 1e passive contact to interrupt both of said magnet circuits.

20. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, a magnet and coiiperating means for advancing said active contact, a control relay, means for closing an energizing circuit for said magnet through contacts of said relay to cause the advance of said active contact over said passive contacts, means for maintaining an energizing circuit for said magnet through other contacts of said relay until said active contact engages an idle passive contact, and means responsive to such engagement to opcrate said relay to cause the denergization of said magnet.

21. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and codperating means for advancing said active contacts, a control relay having contacts under its sole control, means controlled over a single one of said talking strands to close an energizing circuit for said magnet through said contacts of said relay to cause the advance of said active contacts over said passive contacts, and means for operating said relay upon the advance of said active contacts to a position having idle passive contacts to cause the interruption of said magnet circuit.

22. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and coiiperating means for advancing said active'contacts, a control relay having contacts under its sole control, means controlled over a single one of said talking strands t0 close an energizingcircuit for said magnet through said contacts of said relay to cause the advance of said active contacts over said passive contacts, means for operating said relay upon the advance of said active contacts to a position having idle passive contacts to cause the interruption of said magnet circuit, and means controlled by said relay to control the continuity of said talking strands.

23. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and coiiperating means for advancing said active contacts, a control relay having contacts under its sole control, means controlled over a single one of said talking strands to close an energizing circuit for said magnet through said contacts of said relay to cause the advance of said active contacts over said passive contacts, means for maintaining an energizing circuit for said magnet through contacts of said relay until said active contacts are advanced to a position lot lI-ll having idle passive contacts, and means responsive to such advance to operate said relay to cause the deenergization of said magnet.

24. In a telephone system, an automatic switch comprising passive contacts and cm operating active contacts, talking strands extending to certain of said active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contacts. a control relay having contacts under its sole control, means controlled over a single one of said talking strands to close an energizing circuit for said magnet through said contacts of said relay to cause the advance of said active contacts over said passive contacts, means for maintaining an energizing circuit for said magnet through contacts of said relay until said active contacts are advanced to a position having idle passive contacts, means responsive to such advance to operate said relay to cause the denergization of said magnet, and means controlled by said relay to control the continuity of said talking strands.

25. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet. andcofiperating means for advancing said active contacts, a control relay having contacts un der its sole control, talking strands including said contacts of said relay, ,means controlled over a talking strand to close an energizing circuit for said magnet through contacts of said relay to cause the advance of said active contacts over said passive contacts, and means for operating'said felay upon the advance of said active contacts to a position having idle passive contacts.

26. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, 9. magnetand coiiperating means for advancing said active contacts, a control relay having contactsunder its sole control, talking strands including said contacts of said relay, means controlled over a talking strand to close an janergizing circuit for said magnet through icontacts of said relay to cause the advance of said active contacts over passive contacts, means for maintaining an energizing circuit for said magnet through contacts of said relay until said active contacts are advanced to a position having idle passive contacts, and means responsive to the advance of the active contacts to an idle position to cause the operation of said relay.

27. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch assive contacts multiply connected to sai assive contacts, means associated with said other passive contacts for rendering certain of said first-mentioned passive contacts busy, a magnet and cooperating means for advancing said active contact, means controlled over a talking circuit to close an energizing circuit for said mag not, relay-contacts, a relay having sole control of said relay-contacts, moans operative upon an advance of said active contact to close a maintaining circuit for said magnet through certain of said relay-contacts, a busy connection for said active contact including certain of said relay contacts, and means including said relay responsive to the advance of said active contact toan idle position to actuate said relay'contacts to pre vent the further advance of the switch and to render the passive contacts multiply connected to the engaged passive contact busy.

28. In a telephone system, an automatic switch comprising passive contacts and 00- operating active, contacts, talking strands extending to certain of said active contacts, other switch passivecontacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, a magnet and cooperating meansrfor advancing said active contact, means controlled over a talking strand to close an energizing circuit for said magnet, a control relay having contacts under itssole1 control, fmeans operative upon an advance of saidl active contacts to close a maintainingcircuit for said magnet through said contacts'o f said relay, a busy connection for said active contact including, contacts of said relay, and means responsive to the advance of said active contact to an idle position to operate said relay to prevent the further advance of, the switch and to render the passive contacts multiply connected to the engaged passive contact busy.

29. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy,.a magnet and cooperating means for advancing said active contacts, means controlled over I talking trand to. close an energizing circuit for said magnet, a control relay having contacts under its sole control, means operative upon an advance of said active contacts to maintain a circuit for said magnet through said contacts of said relay, a busy connection for one of said active contacts extending through contacts of said relay, talking strands including contacts of said relay. and means for operating said relay as scones said active contacts reach an idle position to stop the further advance of: the switch and to render the corresponding passive contacts of other switches busy and the talking strands continuous.

30. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, a magnet and cooperating means for advancing said active contact, means controlled over atalking strand to close an energizing circuit for said magnet, a control relay, means operative upon an advance of said active contact to maintain a circuit for said magnet throu h normally closed contacts of saidrelay, a usy comm:- tion for said active contact extending through normally open contacts of said relay, and means for energizing said relay, whereby the further ad'vanceof the switch is prevented and'the passive contacts multiply connected to the engaged passive contact are rendered busy.

31. In a telephone system, an automatic switch comprising" passive contacts and cooperating active contacts, talking strands extendin to certainof saidactive contacts, other switch passive contacts multiply connected to said assive contacts, means associated with said other passive contacts for rendering certain of the fii'stinentioned passive contacts busy, a magnet and cooperating means for advancing said active contacts, means controlled over a talking strand to close an energizing circuit for'sald magnet, a control relay, means operative 'upon an advance of said active contacts to close a maintaining circuit for magnet through normally closed contacts of said relay,a busy connection for'one of said active contacts extending through normally open contacts of said relay, talking strands including normally open contacts ofsaid relay, and means for energizing said relay as soon as said active contacts reach an idle position to prevent the further advance of the switch and to render the corresponding passive. contacts of other switches busy and the talkingstrands continuous.

32. In a telephone system, an. automatic itch comprising passive contacts and cooperatingactive contacts, talking strands extendin to certain of said active contacts, other switch passive contacts multiply connected to said passive contacts, means'associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy. a magnet and cooperating means for advancing said active contact, means controlled over a talking strand to close an energizing circuit for said magnet, a control relay having contacts under its sole control, means operative upon an advance of said active contact to maintain a circuit for said magnet through said contacts of said relay a busy connection for said active contact controlled by said relay, and means responsive to the advance of said active contact to an idle position to operate said relay to prevent the further advance of the switch and to render the passive contacts multiply connected to the engaged passive contact busy.

33. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch passive contacts multiply connected to said assive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, a magnet and cooperating means for advancing said active contacts, means controlled over a talking strand to close an energizing circuit for said magnet, relay-contacts, a relay having sole control of said relay-contacts, means operative upon an advance of said active contacts to maintain a circuit for said magnet through certain of said relay-contacts, a busy connection for one of said active contacts in cluding certain of said relay-contacts, means responsivetothe advance of said active contacts to an idle position to operate said relay-contacts to prevent the further advance of theswitch and torender busy the passive contacts multiply connected to the engaged passive contact, and means controlled by said relay-contactsto control the continuity of saidtalkin strands.

34. In a, te ephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy. a magnet and cooperating means for advancing said active contacts, means controlled over a talking strand to close an energizing circuit for said magnet, a control relay having contacts under its'sole control, means operative upon an advance of said active contacts to maintain a circuit for said magnet through said contacts of said relay, a busy connection for one of said active contacts controlled by said relay, means responsive to the advance of said active contacts to an idle position to operate said relay to prevent the furthe advance of the switch and to render bus) the passive contacts multiply connected to the enga pamive contacts, and means controlle by said relay to control the con tinuity of said talking strands.

35. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch assive contacts multiply connected to sai assive contacts, means associated with said other assive contacts for rendering certain of the t-mentioned passive contacts busy, a magnet and cooperating means for advancing said active contact, means controlled over a. talking strand to close an energizing circuit for said magnet, a control relay, means operative upon an advance of said active contact to maintain a circuit for said magnet throu h normally closed contacts of said relay, a busy connection for said active contact controlled through normally open contacts ofsaid relay, and means responsive to the advance of said active contact to an idle position to energize said relay to prevent the further advance of the switch and to render busy the pawve contacts multiply connected to the engaged passive contact; a

36. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the, first-mentioned passive contacts busy, a magnetand coiiperating means for advancing; .said active contacts, means controlled. over a talking strand to close an: energizing circuit for said magnet, a control-,,relay,gmeansroper ative upon an advance ofsafid active contacts to maintain a circuit for said magnet through normally closed: contacts of said relay, a busy connection ion} one of said active, contacts controlledthrough normally open contacts of said relay, means, responsive to the advance of said activeioontacts to an idle position to energize said relay to prevent the further advance of the switch and to render busy the passive contacts multiply connected to the en a ed passive contacts, and means controlled by said relay to control the continuity of said talking strands.

37. In a telephone system, an automatic switch comprising passive contacts and a coiiperating active contact, means outside of said switch for rendering certain of said passive contacts busy, electrically controlled means for advancing said active contact, a control relay, means for initially advancing said active contactby closin a circuit for said advancing means excln ing windings of said relay, means responsive to the initial advance of said active contact to close a control circuit for said advancing means through an energizing winding of said relay, and means for preventing the operation of said relay as long as said active con tact engages busy passive contacts.

38. In a telephone system, an automatic switch comprising passive contacts and a cotiperating active contact, means outside of said switch for renderin certain of said passive contacts busy, electrically controlled means for advancing said active contact, a control relay, means for initially advancing said active contact by closin a circuit for said advancing means excluding windings of said relay, means responsive to the initial advance of said active contact to close a control circuit for said advancing means through an energizing winding of said relay, and means for short-circuiting said winding of said relay as long as said active contact engages busy passive contacts.

39. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, a magnet and co operating means for advancing said active contact, a control relay, means for initially advancing-said active contact by closing a circuit for said magnet, meansresponsive to the initial advance of said active contact to close a circuit through said magnet and said relay. and means for preventing the operation of said relay as long as said active contact engages busy passive contacts.

7 40.11141 telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contact, a control relay, means for initially advancing said active contact by closing a circuit for said magnet, means responsive to the initial advance of said active, contact to close a circuit through said magnet and relay, and means for short-circuiting said relay through said active contact as long as said active contact engages busy passive contacts.

41. In a telephone system, an automatic switch comprising passive contacts and cooperative active contacts, means outside of said switch for rendering certain of said passive contacts busy, electrically controlled means for advancing said active contact, a control relay, talking strands including normally open contacts of said relay, means for initially advancing said active contacts by closing a circuit for said advancing means excluding windings of said relay, means rcsponsive to the inltial advance of said active contact to close a control circuit for said advancing means through an energizing wind ing of said relay, and means for preventing the energization of said relay as long as said active contacts engage busy passive contacts, whereby as soon as an idle passive contact is engaged said relay is energized and said talking strands rendered continuous.

42. In a. telephone system, an automatic switch comprising passive contacts and cooperative active contacts, means outside of said switch for rendering certain of said passive contacts busy, electrically controlled means for advancing said active contact, a control relay, talking strands including normally open contacts of said relay, means for initially advancing said active contacts by closing a circuit for said advancing means excluding windings of said relay, means responsive to the initial advance of said active contact to close a control circuit for said advancing means through an energizing winding of said relay,-Fa nd means for short-circuiting said relay through one of said active contacts as long as it engages busy passive contacts, whereby as soon as an idle passive contact isengaged said relay is energized and said talking'strands rendered continuous.

1 43 111 a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contact, a control relay, talking strands including normally open contacts of said relay, means for causing the initial advance of said active contacts by closing a circuit through'said magnet and excluding windings of said relay, means responsive to the initial advance of said active contact to close a circuit through said magnet and said relay, and means for preventing the energization of said relay as long as said activecontacts engage busy passive contacts, whereby as soon as an idle passive contact is engaged said relay is energized and said talking strands rendered continuous.

44. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contact, a control relay, talking strands including normally open contacts of said relay, means for causing the initial advance of said active contacts by closing a circuit through said magnet and excluding windings of said relay, means responsive to the initial advance of said active contact to close a circuit through said magnet and said relay, and means for short-circuiting said relay through one of said active contacts as long as it engages busy passive contacts, \vhereby as soon as an idle passive contact is engaged, said relay is energized and said talking strands rendered continuous.

45. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contact, a control relay, an oil-normal switch for closing a circuit for said relay upon the initial advance of said active contact, and means for preventing the energization of said relay while said active contact engages busy passive contacts.

46. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contact, a control relay, an off-normal switch for closing a. circuit for said relay upon the initial advance of said active contact, and means for short-circuiting said relay through saidactive'contact while said active contact engages busy passive contacts.

47. In a telephone system, an automatic switch comprising passive contacts and a cooperating active oontact, means outside of said switch for renderingcertain of said contacts busy, means for advancing said active contact, a control relay, an off-normal switch-closing a circuit for said relay upon the'initial advance of said active contact, and means for "preventing the energization of said relay while said active contact engages bu y Passive: contacts.

48. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, a means outside of said switchffoi' rendering-certain of said contacts busy, means foradvancing said active contact, a. controlnlay, an off-normal switch closing a circuit for said relay upon the initial advance of said active contact, and means for short-circuiting said relay through said active contact while said active contact engages busy passive contacts.

-19. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, means for advancing said active contact, a control relay, talking strands including normally open contacts of said relay, an olf-normal switch for closing a circuit for said relay upon the initial advance of said active contact, and means for preventing the energization of said relay as long as said active contacts engage busy passive contacts, whereby as soon as idle passive contacts are engaged, said relay is energized and said talking strands rendered continuous 50. In a telephone system. an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, means for advancing said actiie contact, a control relay, talking strands including normally open contacts of said relayxan oft-normal switch forclosing a circuit for said relay. upon the initial advance of said active contact. and means for short-circuiting said relay through one of said active contacts as long as it engages busy passive contacts. whereby as soon as idle passive contacts are engaged, said relay is energized and. said talking strands rendered continuous.

51. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, a magnet and cooperating means for advancing said active contacts, a control relay, talking strands including normally open contacts of said relay, an ofi"-normal switch for closing a circuit for said relay upon the initial advance of said active contact, and means for preventing the euergization of said relay while said active contacts engage busy s sive contacts, whereby as soon as idle mssive contacts are engaged said relay is energized and said talking strands rendered continuous.

' 52. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, means outside of said switch for rendering certain of said passive contacts busy, amagnet and cooperating means for advancing said active contacts, a control relay, talking strands including normally open contacts of said relay, an off-normal switch for closing a circuit for said relay upon the initial advance of said active contact, and means for shortcircuiting said relay through one of said active contacts as long as busy passive contacts are engaged, whereby as soon as idle passive contacts are engaged said relay is energized and said talking strands rendered continuous.

53. In a telephone system, an automatic switch comprising passive contacts and a 00- operating active Contact, means outside of said switch for rendering certain of said passive contacts busy, a control relay having contacts under its sole control, talking strands including said contacts of said relay, means for causing an initial advance of said active contact by closing a circuit over a sing e one of said talking strands, means for continuing the advance movement of said active contact to an idle passive contact, and then stopping it in engagement therewith, and means whereby said relay maintains said talking strands open while said active contact engages busy passive contacts.

54. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, a control relay, talking strands including normally open contacts of said relay, means for causing an initial advance of said active contact by closing a circuit over a talking strand, means for continuing the advance movement of said active contact to an idle passive contact and then stopping it in engagement therewith, and means for energizing said relay as soon as said active contact engages an idle passive contact.

55. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, means outside of said switch for rendering certain of said passive contacts busy, :1 control relay having contacts under its sole control, talking strands including said contacts of said relay, means for causing an initial advance of said active contact by closing a circuit over a single one of said talking strands, means for continuing the advance movement of said active contact to an idle passive contact and then stopping it in enga ement therewith, and means whereby said relay maintains said talking strands open while said active contact engages busy passive contacts and closed as soon as said active contact engages an idle passive contact.

56. In, a teleph'one system, an automatic switch comprising passive contacts and a cooperating active contact, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, means for advancing said active contact, a control relay, a busy connection controlled by said relay, oif-normal contacts included in said connection, means for operating said contacts during the selecting operation of the switch, and means for operating said relay to apply said connection to a selected idle passive contact and its multiples as soon as such idle contact is selected by said active contact.

57. In a telephone system, an automatic switch comprising passive contacts and a cooperating active eontact, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of said first-mentioned passive contacts busy. means for advancing said active contact, a control relay, a busy connection ineluding normally open contacts of said relay. normally open oil-normal contacts, means for closing said ofl' normal contacts during the selecting operation of the switch, and means for energizing said relay to apply said connection to an idle passive (ontact and its multiples as soon as such idle contact is engaged by said active contact.

58. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, means controlled over a talking strand for initially advancing said active contact, means for continuing its advance until an idle passive contact is encountered and then stopping it in engagement therewith, a control relay having contacts under its sole control, a busy connection controlled by said contacts, and means for operating said relay to apply said connection to a selected i-dle passive contact and its multiples as soon as such idle-contact is selected by said active contact.

59. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, other switch passive contacts multiply connected to said passive contacts, means associated with said other 'a ssive contacts for rendering certain of the t-mentioned passive contacts busy, means'controlled over a talking strand for initiallyadvancing'sa-id active contact, means for continuing its ad Vance until an idle passive 'ooiitiict is'encountered and then sto'ppin' it in engage ment therewith, a control re '5', a busy connection including normally o'pen contacts of said relay, and means for energizing'said relay to apply said connection to an idle pasive'contact and its multiples as soon as such idle contact is engaged by said active contact.

60. In a telephone system, an automatic switch comprising passive contacts, and a coiiperating active contact, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, a control relay having contacts under its sole control, a busy connection controlled by said relay contacts, talking strands having their continuity controlled by said relay, means controlled over a single one of said talking strands for initially advancing said active contact, means for continuing its advance into engagement with an idle passive contact. means whereby said control relay maintains said talking strands open while said active contact engages busy passive contacts, and means whereby said relay closes said talking strands and applies said busy connection to a selected idle passive contact as soon as said idle contact is engaged by said active contact.

61. In a telephone system, an automatic switch comprising passive contacts and a cooperating active contact, other switch passive contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of the first-mentioned passive contacts busy, a control relay having contacts under its sole control, a busy connection including contacts of said relay contacts. talking strands including contacts of said relay, means controlled over a talking strand for initially advancing said active contact, means for continuing its advance into engagement with an idle passive contact, means wh-erebv said control relay maintains said talking s rands open while said active contact engages bus passive contacts, and means whereby said relay closes said talking stran'dsf and applies said busy connection to aselected idle passive contact as soon as said idle contact is engaged by said active contact.

62. In a telephone system, an automatic switch comprising passive contacts and a coo%ating active contact, other switch passi contacts multiply connected to said passive contacts, means associated with said other passive contacts for rendering certain of said first-mentioned passive contacts busy, acontrolrelay, a'-busy connection including normally openeontaets of said relay, talking contacts including normally open contacts of *s'aidrela'y, means controlled over a talkingstiand for initially advancing said active contact, means-for continuing its advance intdengagement with an idle passive Contact, means forener'giz'ing said control relay to close said talking strands and to apply the busy connection to the engaged passive contact only upon the engagement of said active contact with an idle passive contact.

63. In a telephone system, an automatic switch comprising passivecontacts: arranged in groups and a cooperatingactive contact, a primary magnet and associated mechanism for advancing said active contact to positions corresponding to said groups, a secondary magnet and associated mechanism for advancing said active contact over passive contacts in said groups, means outside of said switch for rendering certain of said passive contacts busy, means for energizing said primary magnet to produce the primary movement of Said active contact. a control relay having contacts under its sole control, means for closing a controlling circult for said secondary magnet through said 'for advancing said active contact to psitions corresponding to said groups, a secondary magnet and associated mechanism for advancing said active contact over passive contacts in said groups, means outside of said switch for rendering certain of said passive contact-s busy, a control relay, means for closing a circuit for said primary magnet through normally closed contacts of said relay. means for closing a circuit for said secondary magnet also through normally closed contacts of said relay, and means for energizin said relay upon the engagement of said active contact with an idle passive contact.

65. In a telephone system, an automatic switch comprising passive contacts arranged in groups and a coperating active contact, a primary magnet and associated mechanism for advancing said active contact to positions corresponding to said groups, a secondury magnet and associated mechanism for advancing said active contact over passive cont cts in said groups, means outside of said switch for rendering certain of said passive contacts busy, a control relay, means for closing a circuit for said primary magnet through normally closed contacts of said relay. means for closing a circuit for said secondary magnet also through normally closed contacts'of said relay, talking strands including normally open contacts of said relay, and means for energizing saidrelay upoii the engagement of said active contact with an idle passive contact.

66. In a telephone system, an automatic switch comprising passive contacts'arranged in groups and a cooperating active contact, a primary magnet and associated mechanism for advancing said active contact to positions corresponding to said groups a secondary magnet and associated mechanism for advancing sa d active contact over passive contacts in said groups, means outside of said swit h for rendering certain of said passive contacts busy, talking strands, a relay having contacts under its sole control for controlling said primary and secondary magnets and talking strands, and means for operating said relay upon the engagement of said active contact with an idle passive con tact.

67, In a telephone system, an automatic switch comprising passive contacts arranged in groups and a coiiperating active contact,

a primary magnet and associated mechanism for advancing said active contact to positions corresponding to said groups, a secondarv magnet and associated mechanism for advancing said active contact over said passive contacts in said groups, means outside of said switch for rendering certain of said passive contacts busy. talhing strands, a busy connection for said active contact. a relay having contacts under its sole control for controlling said primary and secondary magnets and said talking strands and busy connection, and means for operating said relay upon the engagement of said active contact with an idle passive contact.

68. In a telephone system, an automatic switch comprising passive contacts arranged in groups and a cotiperating active contact, a primary magnet and associated mechanism for advancing said active contact to positions corresponding to said groups, a second ary magnet and associated mechanism for advancing said active contact over passive contacts in said groups. means outside of said switch for rendering certain of said passive contacts busy, talking strands, a relay having contacts under its sole control for controlling said secondary magnet and talking strands, and means for operating said relay upon the engagement of said active contact with an idle passive contact.

69. In a telephone system. an automatic switch comprising passive contacts arranged in groups and a cotiperating active contact, a primary magnet and associated mechanism for advancing said active contact to positions corresponding to saidgroups, a secondary magnet and associated mechanism for advancing said active contact over passive contacts in said groups, means outside of said switch for rendering certain of said passive contacts busy, talking strands, a busy connection for said active contact, a relay having contacts under its sole control for controlling said secondary magnet and said talking strands and busy connection, and means for operating said relay upon the engagement of said active contact with an idle passive contact.

'70. In a telephone system, an automatic switch comprising passive contacts arranged in groups and a coiiperating active contact, aprianary magnet and associated mechanism for advancing said active contact to positions corresponding to Fflld growls. a secondnry magnet and associated mechanism for advancing said active contact over passive contacts in said groups, means outside of said switch for rendering certain of said passive contacts busy, talking strands, u re lay having contacts under its sole control for controlling said primary magnet and talking strands, and means for operating said relay upon the engagement of said active contact with an idle passive contact.

T1. In a telescope system, an automatic switch comprising passive contacts arranged in groups and a cooperating active contact, a primary magnet and associated mechanism for advancing said active contact to positions corresponding to said groups, a secondary magnet and associated mechanism for advancing said active contact over passive contacts in said groups, means outside of said switch for rendering certain of said passive contacts busy, talking strands, a busy connection for said active contact, a relay having contacts under its sole control for controlling said primary magnet and said talking strands and busy connection, and means for operating said relay upon the engagement of said active contact with an idle passive contact.

72. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said contacts, means controlled over one of said strands to advance said active contact over said passive contacts to a desired position, a control electromagnet, means for energizing said magnet as soon as said active contact reaches said desired position, means for denergizing said magnet, and means for restoring said active contact to normal upon the deenergization of said magnet.

73. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to'certain of said active contacts, means outside of said switch for rendering certain of said passive contacts busy, means controlled over a talking strand to advance said active contact over said passive contacts until an idle passive contact is encountercd, a control electromagnet, means for energizing said magnet as soon as said active contact reaches an idle passive contact, means for denergizing said magnet, and means for restoring said active contact to normal upon the denergization of said magnet.

74. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands ex tending to certain of said active contacts, means controlled over a talking strand to advance said active contact over said passive contacts to a desired position, a control relay having normally open contacts including said talking strands, means for energizing said relay upon the movement of said active contact to said desired position, means for denergizing said relay, and means for restoring said active contact to normal upon the denergization of said relay.

T5. In a telephone system, an automatic switch comprising passive contacts and co operating active contacts, talking strands 76. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, means controlled over a talking strand to advance said active contact over said passive contacts to a desired position, a control relay, a busy connection to said active contact including contacts of said relay, means for energizing said relay to apply said busy connection, means for denergizing said relay, and means for restoring said active contact to normal upon the de e'nergization of said relay.

77. In a telephone system, an automatic switch comprising passive contacts and cooperating active contacts, talking strands extending to certain of said active contacts, means outside of said switch for rendering certain of said passive contacts busy, means controlled over a talking strand to advance said active contact over said passive contacts until an idle-passive contact is encountered, a control relay, a busy connection to said active contact including contacts of said relay, means for energizing said relay upon the engagement of said active contact with an idle passive contact, means for denergizing said relay, and means for restoring saidactive contact to normal upon the deenergization of said relay.

78. In a telephone system, a plurality of operatively related automatic switches, means for successively actuating two of said switches for extending a circuit through them, an electromagnet associated with one of said actuated switches. means operated upon the deenergization of said electromagnet to cause the release of the associated switch, means associated with the other actuated switch for energizing said electromagnet responsive to the establishment of the circuit through said switches, and means for denergizing said electromagnet.

79. In a telephone system, a plurality of operatively related automatic switches, means for successively actuating two of said switches for extending a circuit through them, an electromagnct associated with one of said actuated switches, means operated upon the denergization of said electromagnet to cause the release of the associated switch, and means associated with the other actuated switch for energizing said electromagnet responsive to the establishment of the circuit through said switches and deenergizing said magnet when it is desired to interrupt said circuit.

80. In a telephone system, a plurality of .operatively related automatic switches,

interrupt said switch circuit.

81. In a telephone system, two automatic switches, associated conductors, means for operating said switches to unite said condnctors into a continuous circuit, an electromagnet associated with each switch, means for energizing said magnets upon the said operation of said switches, means for deenergizing one of said magnets in response to the deen'ergization of the other, means for dee'nergi'zing the latter, and means for releasing said switches individually in response to the deinergization of said magnets.

82. In a telephone system, two automatic switches, associated conductors,means for operating said switches to unite said conductors into a continuous circuit, an electromagnet associatedwith each switch, means for completing an energizing circuit for one of said magnetsupon thesaid operation of the corresponding switch, means for complating an energizing circuit for the second magnet through contacts of said firstmag-- net upon the said operation of the second switch, means for denergizing said first 'magnet to thereby denergize said second magnet, and means for releasing said switches individually in response to the deencrgization of said magnets.

83. A telephone system including a pair of connected telephone lines, a plurality of directively operable selective switches having contacts included in the talking circuit, electromagnets for said switches respectively for restoring purposes, means for holding said magnets energized while connection exists, and apparatus for denergizing said magnets when disconnection is desired to restore the respective switches to normal.

84. A telephone system including a pair of connected telephone lines, a plurality of selective switches having contacts included in the talking circuit, an additional contact for one of said switches not included in the talking circuit serving to protect said cirsuit against intrusion, an electromagnet for another of said switches held energized during conversation over a circuit including said additional contact, and mechanism for deinergizing said last-mentioned electromagnet when disconnection is desired to restore said other switch to normal.

85. In a telephone system, an automatic switch having active and passive contacts, means for advancing said active contact, other similar coiiperating active and passive switch contacts, means for closing a release circuit for said switch through said other active and passive contacts responsive to the completion of the advance movement of said switch, and means for restoring said active contact to normal by interrupting said release circuit.

36. In a telephone system, an automatic switch having active and passive contacts, means for advancing said active contact, other similar cotiperating active and passive switch contacts, means for closing a release circuit for said switch including said other active and passive contacts upon the completion of the advance movement of said switch, and means for restoring said active contact to normal by separating said other active and passive contacts.

87. In a telephone system, an automatic switch having active and passive contacts, a magnet for advancing said active contact, arelease magnet, an associated plug and jack, means for closing a release circuit for said switch "serially through said release magnet and said plug and jack, and means for restoring said active contact to normal by withdrawing said plug from said jack.

88. In a telephone system, an automatic switch having active and passive contacts, means for advancing said active contact, another passive contact, a terminal for es tablishing connection with said other passive contact, means for closing a release circuit for said switch through said other passive contactand said terminal responsive to the completion of theadvance movement of said switch, and means for restoring said active contact to normal by interrupting said release circuit.

89. In a' telephone system, an automatic switch having active and passive contacts, means for advancing said active contact, another passive contact, a terminal for establishing connection with said other passive contact, means for closing a release ciredit for said switch through said other passive contact and said terminal upon the tion to interrupt said former rglease circuit,

completion of the advance movement of said switch, and means for restoring said active contact to normal by interrupting said release circuit at said terminal and other passive contact.

90. In a telephone system, an automatic trunk selector switch having active and possive contacts, means for advancing said active contact, a second trunk selector switch having a like passive contact, a wiper terminal for establishing connection with said other passive contact, means for closing a release circuit through said terminal and second passive contact responsive to; their connection, a relay for controlling said release circuit, and means for restoring said active contact and wiper terminal to normal upon the interruption of said release circuit.

91. In a telephone system, an automatic switch havin active and passive contacts, means for advancing said active contact, another switch having similar cooperating active and passive contacts, means for closing a release circuit for said former switch through active and passive contacts of said latter switch, a relay associated with said latter switch for controlling said release circuit, means for actuating said relay to interrupt said release circuit, and means for restoring the active contact of the former switch-to normal upon the interrupt on of said release circuit.

92. Ina telephone system, an automatic switch having active and passive contacts, means for advancing said active contact, another switch having similar cooperating active and passive contacts, means or closing. a release circuitfor said former switch through active and passive contacts oi said latter switch, anothfil zpassilte contact, means for closing a-rcleasecircuit for said latter switch through said other' passivecontact, means for interrupting sa ddatter release, circuit, means responsive to such interrup and means for restoring the act ve contact, of each switch to normal upon the interruption of its release circuit.

9,3. In a telephone system, an automatic trunk selector SWitChr havingactive and passive contacts, means ifion advancing said active contact, a. release circuit; for, said switch normally openat, tw pointsof control, 03 normal contacts-operatedib the advance of said active contact to can Said circuit at one control point, a second trunk selector switch having a contact and coolperating wiper included in the circuit at t e second control point, and means for subsequently exercising a. control from the other control point so as to cause the res torationv of said active Contact to normal,

94.,Inn telephone system, an automatic trunk selector switch having active and passive contacts, means for advancing said active contact, another automatic trunk selector switch passive contact, a wiper terminal for establishing connection with said other passive contact, a release circuit for said switch normally open at said other passive contact and at another point, ofi' normal contacts operated by the advance of said active contact to close said circuit .at said other point, and means for causing the restoration of said active contact to normal in response to a control occasioned by said terminal and associated passive contact.

95. In a telephone system, an automatic trunk selector switch having active and passive contacts, means for advancing said active contact, a release circuit for said switch having its continuity controllable at two points, a second automatic trunk selector switch, oflf normal contacts operated by the advance of the first switch to exercise control of said release circuit at one of said points, and means associated with said second switch for exercising control of said release circuit at the other control point.

96. In a telephone system, an automatic trunk selector switch having active and pets sive contacts, means for advancing said active contact, a. release circuit for said switch having its continuity controllable at two points, off normal contacts operated by the advance of sa d switch to exercise control of said release circuit atone of said points, means including an automatic selector for exercising the, control at. the second p i n m a s for, caus ng the r s a ion of the active contact to normal by the o n f sa d r l a e. icada 97 In a e ephone system, an automatic trunk selector switch having active and .passive contact means for advancing said active contact, an electro1nagnet and mechamsm for restorung active contact to normal, an enengizing'circuit for said electromagnet controlled at two" points, means operated bv the advance of said active contact to close said circuitat one point, means includ ng a second trunk selector switch for closing said circuit at the other point, and talking strands controlled by contacts of said tromagnet.

98. A telephone, system comprising a plurality of central ofl ices, and means for interconnecting said ofiices by Conversational circuits ncludin selector switches located in one of said 0 ces and passive contacts arranged in groups severally assigned for connection to different distant central ofiices, trunks extending from said several groups to said several central oflices, and manually operated switching equipments in which said tr n s terminate at said distant central ii iiices for extending said trunks to telephone mes.

99. A telephone system comprising a plu- 

